1. Field of the Invention
This invention relates to improvement of a communication control method in an image forming system in which a sheet processing apparatus of a different type is connected with an image forming apparatus.
2. Description of Related Art
The image forming apparatus can be used as a printing apparatus because various types of bookbinding processing become possible by being connected with various types of sheet processing apparatuses to form the image forming system. For example, saddle stitching bookbinding can be conducted by applying a stapling process to the crease portion of the sheet bundle made by folding sheets at the center of the sheets. The square back processing which produces a condition similar to the un-sewn binding is possible by applying pressure to the spine portion of a saddle stitched sheet bundle with a roller or the like and by forming a crease at the corner to produce the spine portion.
As a pre-processing to make such a crease, a line is made by using a line-making device called by the name of a creaser to apply a line-making process at the place where a crease is to be produced. The performance of the folding process after the line-making process has an advantage to prevent the crease from swelling even if multiple sheets are gathered and folded. Further, by the line-making process before the folding process, there is another advantage to prevent a toner from removing at the crease portion on the sheet convex surface during the folding process.
When various bookbinding processes like these are conducted, several sheet processing apparatuses having different functions are connected to the back of the image forming apparatus in series. Then a product subjected to bookbinding of the desired condition is obtained by applying the process to sheets on which images have been formed, by the sheet processing apparatus.
In an image forming system constituted by such an image forming apparatus and a sheet processing apparatus, it is necessary to transmit various control signals and sensor detection results between the apparatuses as well as to convey sheets from the top apparatus to the last apparatus. Normally an image forming apparatus and sheet processing apparatus are connected in series and the information is transmitted through a communication function of each apparatus.
As the contents of the communication, for using sufficient functions of various complicated sheet processes by the sheet processing apparatus or for operating in cooperation with each other at high productivity as a whole system, various types of and massive information such as a sheet discharge timing, a sheet type, an apparatus condition need to be transmitted without delay. Therefore, a high speed serial communication is used for communication between apparatuses to transmit massive data.
On the other hand, recently various sheet processing apparatuses are required. For this reason, it is becoming more difficult that only apparatuses of one manufacturer are used for sheet processing apparatuses arranged in order to cope with various processes. Accordingly, for the image forming system to be used as a printing apparatus, it is desirable that a sheet processing apparatus developed by another manufacturer (hereinafter, referred to as “third-vender sheet processing apparatus”) can be connected with an image forming apparatus and a sheet processing apparatus which are main parts.
For methods to cope with these problems, various proposals are provided in Japanese Unexamined Patent Application Publication Nos. 2006-350961 and 2009-271761. In the Japanese Unexamined Patent Application Publication No. 2006-350961, minimum information needed by the sheet processing apparatus is transmitted by the parallel communication which has been used widely in general in the past to cope with the problems. The parallel communication is commonly used in the field of the printer and is a de facto standard, however only the minimum information for the operation can be transmitted because it is simple.
In the Japanese Unexamined Patent Application Publication No. 2009-271761, proposed is a technique for using adaptively an in-line finisher and a near-line finisher physically connected with an image forming apparatus in series. The in-line finisher is a sheet processing apparatus connected with the image forming apparatus in series. The near-line finisher is a sheet processing apparatus which is not physically connected with the image forming apparatus and is arranged in the vicinity. Therefore, a technique in which the print job is divided or converted according to which finisher is to be used, is proposed.
When a third-vender sheet processing apparatus is connected with an image forming apparatus, it is common that a genuine sheet processing apparatus is connected directly at the rear of the image forming apparatus and the third-vender sheet processing apparatus is connected at the rear of the genuine sheet processing apparatus. The genuine sheet processing apparatus is a sheet processing apparatus of the same manufacturer as the image forming apparatus. Four reasons are explained as follows.
Reason 1: The third-vender sheet processing apparatus tends to restrict the contents of possible sheet processes. For example, a certain third-vender sheet processing apparatus only conducts the discharge of saddle stitching booklets and cannot carry out the straight discharge which does not conduct the discharge of saddle stitching booklets. The third-vender sheet processing apparatus is often constructed to be connected as the final stage. Thus it is necessary to provide a genuine sheet processing apparatus having a function of a sub-tray discharge between the image forming apparatus and the third-vender sheet processing apparatus.
Reason 2: The speed of input conveyance into the third-vender sheet processing apparatus tends to be fixed. In this case, the speed adjustment is necessary in the previous stage. Thus, a genuine sheet processing apparatus whose speed is adjustable and which has, for example, a function of a relay unit or the like is necessary to be connected between the image forming apparatus and the third-vender sheet processing apparatus.
Reason 3: The height of the input position of the third-vender sheet processing apparatus tends to be unmatched with the discharge position of the image forming apparatus. Thus it is necessary to provide a genuine sheet processing apparatus whose heights of input and output positions are adjustable between the image forming apparatus and the third-vender sheet processing apparatus.
Reason 4: Only one sheet processing apparatus can be connected directly after the image forming apparatus regardless of whether it is the third-vender sheet processing apparatus or the genuine sheet processing apparatus. Thus even if an interface for the third-vender sheet processing apparatus (for example, the parallel interface having high versatility) is provided on the image forming apparatus, when a genuine sheet processing apparatus is connected with the image forming apparatus with the serial interface, which occupies the majority of the use methods, the parallel interface becomes useless.
Because of the above four reasons, it becomes necessary that for example, a genuine sheet processing apparatus for adjusting the conveyance speed and a genuine sheet processing apparatus for securing a discharge on a sub-tray need to be connected between an image forming apparatus and a third-vender sheet processing apparatus.
In this case, the connection is made as follows. The image forming apparatus and the genuine sheet processing apparatus are connected so that information is transmitted by the serial communication between them. When multiple genuine sheet processing apparatuses exist, they are connected so that information is transmitted between a genuine sheet processing apparatus and a genuine sheet processing apparatus through the serial communication. The genuine sheet processing apparatus and third-vender sheet processing apparatus are connected so that information is transmitted through the parallel communication.
When the connection is arranged for communication as described above, the following problems newly occur.
Problem 1: Detailed information regarding the sheet processing, for example, information on a sheet length can be transmitted because assignment of information is possible when the serial communication is used. However, when the parallel communication is used, detailed information regarding sheet processing or the like cannot be assigned and cannot be transmitted. Thus an operation of mode setting is necessary between the apparatuses in advance before the start of operation.
Problem 2: Detailed information regarding apparatus operation conditions, for example, information on positions or contents of the jam can be transmitted at the time of occurrence of the jam when the serial communication is used. However, detailed information regarding an apparatus operation condition cannot be transmitted through the parallel communication. Therefore, information on occurrence of some abnormality in the third-vender sheet processing apparatus is transmitted. However, to know the detailed contents of the abnormality which has occurred, the operator needs to see the operation panel of the third-vender sheet processing apparatus.
Problem 3: The imposition information or prohibition rule information of the third-vender sheet processing apparatus cannot be transmitted to the image forming apparatus by the parallel communication. For this reason, the mode setting based on the third-vender sheet processing apparatus need to be conducted on the image forming apparatus side before the start of operation.
Problem 4: Many third-vender sheet processing apparatuses are structured to be used not only as an in-line finisher but also as a near-line finisher. However, under conditions where the third-vender sheet processing apparatus is connected as an in-line finisher, when the power of the image forming apparatus is turned off, the power of the third-vender sheet processing apparatus is also turned off simultaneously. For this reason, the third-vender sheet processing apparatus cannot be used independently as a near-line finisher.
As described above, a problem of worsening the usage occurs when the third-vender sheet processing apparatus is connected to an image forming apparatus. Though the above specific examples shows that the third-vender sheet processing apparatus transmits information through the parallel communication and the image forming apparatus and the genuine sheet processing apparatus transmit information by the serial communication, the situation is not limited to these. For example, when an image forming apparatus and a genuine sheet processing apparatus transmit information through a high-speed serial communication or the third-vender sheet processing apparatus transmits information through a low-speed serial communication, problems similar to the above-described ones can occur. Further, when an image forming apparatus and a genuine sheet processing apparatus transmit information by a serial communication which can deal with various data and a third-vender sheet processing apparatus transmits information by a serial communication which deal with minimum data, problems similar to the above-described ones can occur.
In the above description, “information cannot be transmitted” includes not only the case where information cannot be transmitted because of difference of communication protocols, but also the case where amount of assigned commands or data is small because the defined information contents are restricted. Similarly, “information cannot be transmitted” includes the case where precision or the number of digits of numerical value of the handled information is different. Further similarly “information cannot be transmitted” includes the case where the communication of the sheet processing is not at an appropriate timing because the communication speed is low.
Further in the above description, though specific examples of third-vender sheet processing apparatus are described, it is not restricted to them. For example, even in the case of products manufactured by the same manufactures, when a high-performance apparatus in which various functions including a communication function is enlarged and a low-performance apparatus in which various functions including a communication function is restricted are connected, there is probability of occurrence of the similar problems.
That is to say, to an image forming apparatus as an upstream apparatus, an apparatus of a different type whose information communication is restricted due to the communication (third-vender sheet processing apparatus or sheet processing apparatus of the same manufacturer but of a different type) is connected as the downstream apparatus, it has been made clear that various types of malfunctioning occur.
The present invention is achieved in view of these problems, and has an objective to provide an image forming system and an image forming system communication control method which can improve the operation conditions without generating restrictions in the image forming system in which an apparatus of a different type is connected as a downstream apparatus.
The present invention is achieved in view of these problems, and has an objective to provide an image forming system and an image forming system communication control method which allows the downstream apparatus to operate alone independently of the upstream apparatus without operational restrictions in the image forming system in which an apparatus of a different type is connected as a downstream apparatus.